ios - 通用问题，有什么建议吗？

// UITableView + .Swift扩展

extension UITableView {

 func cellForModel<T: CellViewModel>(at: IndexPath, model: T) -> T.CellType  {
    let cell: T.CellType = dequeueReusableCell()
    *let t = model as! T.CellType.ModelType*
    cell.setupModel(model: t)
    return cell
  }

  func dequeueReusableCell<T: ReusableCell>() -> T {
    print(T.reuseIdentifier())
    let temp = self.dequeueReusableCell(withIdentifier: T.reuseIdentifier())

    return temp as! T
  }
}

// CellViewModel.Swift

protocol CellViewModel where Self: NSObject, CellType: ReusableCell {
  associatedtype CellType
}

// ReusableCell.Swift

protocol ReusableCell where Self: UITableViewCell, ModelType: CellViewModel {
  associatedtype ModelType
  static func reuseIdentifier() -> String
  func setupModel(model: ModelType)
  var cell: UITableViewCell { get }
}

extension ReusableCell {
  static func reuseIdentifier() -> String {
    return String(describing: Self.self)
  }
  var cell: UITableViewCell {
    return self as UITableViewCell
  }
}

我的问题是，为什么我需要在UITableView Extension中对此进行let t = model as! T.CellType.ModelType而不是仅仅将模型传递给setupModel(model: ModelType)函数。

最佳答案

您需要将约束CellType.ModelType == Self添加到CellViewModel

protocol CellViewModel where Self: NSObject, CellType: ReusableCell, CellType.ModelType == Self {
    associatedtype CellType
}